A control group who ate a low-cal, high-carb vegetarian diet that included dairy and egg products lost a similar amount but showed less improvement in coronary risk factors, David Jenkins, M.D., of the University of Toronto reported with colleagues the June 8 Archives of Internal Medicine.

Weight loss after four weeks was similar in the two groups -- about 8.6 pounds for the so-called "Eco-Atkins" diet and 9.2 pounds in the control group.

But participants who received the low-carbohydrate diet had greater reductions in LDL cholesterol (20.4% versus 12.3%, P=0.002) and in the ratio of total to HDL cholesterol (P=0.004).

They also had significantly better improvements in total cholesterol (P=0.001), triglycerides (P=0.02), apolipoprotein B (P=0.001), and the ratio of apolipoprotein B to apolipoprotein AI (P=0.001).

There were slightly greater reductions in systolic and diastolic blood pressure, but no differences in HDL cholesterol.

"A plant-based, low-carbohydrate diet high in vegetable proteins and oils may be an effective option in treating those with dyslipidemia for whom both weight loss and lower LDL cholesterol concentrations are treatment goals," the researchers concluded.

But researchers noted that these diets have also been associated with increased LDL cholesterol concentrations.

But replacing meat with vegetables as the source of protein had not been studied, they said.

So they randomized 24 men and women who were overweight (BMI >27 kg/m2) and had an LDL cholesterol level greater than 131 mg/dL to a diet low in carbohydrates and calories but high in proteins from gluten, soy, nuts, fruits, vegetables, cereals, and vegetable oils.

About a quarter of the calories (26%) came from carbohydrates, 31% came from protein, and 43% came from fat. The researchers called this the Eco-Atkins diet.

Another 23 participants were randomized to a low-calorie, high-carbohydrate vegetarian diet based on low-fat dairy and whole-grain products. More than half of the calories (58%) came from carbohydrates, 16% came from protein, and 25% came from fat.

The researchers prepared and supplied all meals, and participants in both groups received about 60% of their estimated calorie requirements.

Among other researchers, reaction to the study was generally positive.

It "shows, again, that weight loss is about calories, not macronutrient distribution," commented David Katz, M.D., M.P.H., director of Yale University's Prevention Research Center.

"The myth that other factors drive weight loss just won't die, so I hope this drives another nail in its coffin," said Dr. Katz, who was not involved in the study.

Dr. Jenkins and colleagues said there are still many outstanding questions about the low-carbohydrate diet, including the possible benefit of replacing some of the vegetable protein with vegetable oil and whether there is an optimal carbohydrate load.

The study "provides insight into debatably more effective and possibly safer tactics for designing higher-protein diets for weight loss and cardiovascular risk reduction," according to an accompanying editorial by Katherine Tuttle, M.D., and Joan Milton, R.D., at the University of Washington School of Medicine in Spokane, Wash.

"However," they wrote, "it is premature to recommend the Eco-Atkins diet as a weight loss diet of choice without confirmation of its efficacy in larger studies of more diverse and higher-risk individuals. Long-term studies are also essential to ascertain both sustainability and safety."

In addition, the efficacy of the diet needs to be assessed in a more realistic setting where patients prepare their own meals, they wrote.

Dr. Katz noted that the study "does not show the superiority of [the Eco-Atkins] diet over an optimized, higher-carbohydrate diet which may be far more familiar, palatable, and convenient."

Others were amused or even offended by the term "Eco-Diet."

"Even when wrapped up in a trendy, sustainably green packaging, the Atkins diet is still the Atkins diet," said Jackie Newgent, R.D., author of Big Green Cookbook. "The tempting 'eco' label on this still unbalanced, way-too-high protein diet is basically greenwashing."

The study was supported by Solae, a soy food company, Loblaw Companies Limited, and the Canadian Research Chair Program of the Federal Government of Canada. One of the study authors received a Canadian Institutes of Health Research Doctoral Research Award.

Dr. Jenkins has served on the scientific advisory board of Unilever, the Sanitarium Company, and the California Strawberry Commission, received research grants from Loblaws, Unilever, Barilla, and the Almond Board of California, served on the speakers' panel for the Almond Board of California, and received honoraria for scientific advice from the Almond Board of California, Barilla, Unilever Canada, and Solae. His co-authors reported potential conflicts of interest with the Almond Board of California, Unilever, and Loblaws. One of the study authors is a past employee of Solae and a current employee of Kellogg's. One of the other authors is an employee of Solae.

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